Reddy Kasala Prabhakar, Dama Srikanth, Mhamane Nitin B, Ghosalya Manoj K, Raja Thirumalaiswamy, Satyanarayana Chilukuri V, Gopinath Chinnakonda S
Catalysis Division, CSIR-National Chemical Laboratory, Dr. Homi Bhabha Road, Pune 411 008, India.
Dalton Trans. 2019 Aug 28;48(32):12199-12209. doi: 10.1039/c9dt01774g. Epub 2019 Jul 23.
Carbon dioxide is a greenhouse gas, and needs to be converted into one of the useful feedstocks, such as carbon monoxide and methanol. We demonstrate the reduction of CO with H as a reducing agent, via a reverse water gas shift (RWGS) reaction, by using a potential and low cost MoC catalyst. MoC was evaluated for CO hydrogenation at ambient pressure as a function of temperature, and CO : H ratio at a gas hourly space velocity (GHSV) of 20 000 h. It is demonstrated that the MoC catalyst with 1 : 3 ratio of CO : H is highly active (58% CO conversion) and selective (62%) towards CO at 723 K at ambient pressure. Both properties (basicity and redox properties) and high catalytic activity observed with MoC around 700 K correlate well and indicate a strong synergy among them towards CO activation. X-ray diffraction and Raman analysis show that the MoC catalyst remains in the β-MoC form before and after the reaction. The mechanistic aspects of the RWGS reaction were determined by near-ambient pressure X-ray photoelectron spectroscopy (NAPXPS) with in situ generated MoC from carburization of Mo-metal foil. NAPXPS measurements were carried out at near ambient pressure (0.1 mbar) and various temperatures. Throughout the reaction, no significant changes in the Mo oxidation state (of MoC) were observed indicating that the catalyst is highly stable; C and O 1s spectral results indicate the oxycarbide species as an active intermediate for RWGS. A good correlation is observed between catalytic activity from atmospheric pressure reactors and the electronic structure details derived from NAPXPS results, which establishes the structure-activity correlation.
二氧化碳是一种温室气体，需要将其转化为有用的原料之一，如一氧化碳和甲醇。我们通过使用一种有潜力且低成本的碳化钼（MoC）催化剂，经由逆水煤气变换（RWGS）反应，证明了以氢气作为还原剂对二氧化碳进行还原。在环境压力下，以温度以及在气体时空速（GHSV）为20000 h⁻¹时的CO∶H比为函数，对碳化钼进行了CO加氢评估。结果表明，在环境压力下723 K时，CO∶H比为1∶3的碳化钼催化剂对CO具有高活性（CO转化率为58%）和高选择性（62%）。在700 K左右观察到的碳化钼的性质（碱性和氧化还原性质）与高催化活性之间具有良好的相关性，这表明它们之间对CO活化具有很强的协同作用。X射线衍射和拉曼分析表明，碳化钼催化剂在反应前后均保持β-MoC形式。通过近常压X射线光电子能谱（NAPXPS），利用金属钼箔渗碳原位生成的碳化钼，确定了RWGS反应的机理。NAPXPS测量是在近常压（0.1 mbar）和不同温度下进行的。在整个反应过程中，未观察到碳化钼的钼氧化态有显著变化，这表明该催化剂具有高度稳定性；C和O 1s光谱结果表明，氧碳化物物种是RWGS的活性中间体。在大气压反应器中的催化活性与从NAPXPS结果得出的电子结构细节之间观察到良好的相关性，这建立了结构-活性关系。
